Passive Reactor Cooling via Gravity-Driven Decay Heat Rejection
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Solution Overview
Problem
Current nuclear reactor containment systems rely on pumped heat rejection systems that require power sources, making them vulnerable during station blackouts or loss-of-coolant accidents, and lack efficient means to manage internal pressure and heat rejection.
Innovation Solution
A passive cooling system using gravity-driven fluid flow and heat exchangers to reject decay heat without relying on electric power, incorporating a closed flow loop with a heat exchanger and an annular reservoir for heat dissipation, and an auxiliary air cooling system for prolonged operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If pumped heat rejection systems are used to reject decay heat, then heat rejection efficiency is improved, but system reliability deteriorates due to dependence on power sources
Solution Approach 1:
The patent replaces the mechanical pump-based heat rejection system with a passive natural convection system. The cooling fluid circulates through the containment structure and heat exchangers driven by natural density differences (hot fluid rises, cool fluid sinks) rather than mechanical pumps, eliminating the need for external power sources while maintaining heat rejection capability.
Solution Approach 2:
The containment structure's own thermal energy drives the cooling system. The temperature differential between the hot containment interior and cooler exterior automatically generates fluid circulation through natural convection, allowing the system to self-regulate and operate indefinitely without external power input.
2Strength
If massive reinforced concrete containment structures are built to withstand aircraft impact, then structural strength is improved, but heat rejection capability deteriorates due to thermal insulation properties
Solution Approach 1:
The containment structure is segmented into functional zones: the massive concrete provides structural strength and impact resistance, while integrated heat exchanger surfaces and fluid circulation pathways are distributed throughout the structure to provide heat rejection. This segmentation allows each component to optimize its primary function without compromising the other.
Solution Approach 2:
The patent merges the structural containment function with the heat rejection function by integrating cooling fluid circulation pathways and heat exchanger surfaces directly into the containment structure. The concrete structure serves dual purposes: providing mechanical strength and acting as a heat transfer medium to the external environment.
3Loss of energy
If active pumped cooling systems are used, then cooling efficiency is improved, but ease of operation deteriorates due to requirement for power sources and complex control
Solution Approach 1:
The passive natural convection system requires no operator intervention or external power sources. The system automatically responds to temperature differentials, circulating cooling fluid through the containment structure and heat exchangers based on real-time thermal conditions, providing simple and reliable operation during emergency scenarios.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables efficient and prolonged heat rejection and pressure management during accidents, ensuring containment integrity without the need for power sources, allowing the system to operate indefinitely and maintain structural integrity.
Implementation Method 1
The cooling system relies entirely on gravity and varying fluid densities to extract and induce flow of cooling water through the system
Implementation Method 2
a heat exchanger disposed in the containment vessel, the heat exchanger in fluid communication with the reactor well via a closed flow loop
Implementation Method 3
the tank is configured and operable to flood the reactor well with cooling water which is converted into steam by heat from the fuel core
Implementation Method 4
the steam condenses in the heat exchanger forming condensate, and the condensate flows via gravity back to the reactor well
Data Source
AI summary
A nuclear reactor cooling system with passive cooling capabilities operable during a loss-of-coolant accident (LOCA) without available electric power. The system includes a reactor vessel with nuclear fuel core located in a reactor well. An in-containment water storage tank is fluidly coupled to the reactor well and holds an inventory of cooling water. During a LOCA event, the tank floods the reactor well with water. Eventually, the water heated by decay heat from the reactor vaporizes producing steam. The steam flows to an in-containment heat exchanger and condenses. The condensate is returned to the reactor well in a closed flow loop system in which flow may circulate solely via gravity from changes in phase and density of the water. In one embodiment, the heat exchanger may be an array of heat dissipater ducts mounted on the wall of the inner containment vessel surrounded by a heat sink.